Joint power and work in an elite sprinter at maximum velocity

Mechanical power and work reveal the important aspects of muscle interactions in performance. Leg joint power patterns during ground-contact have been documented in sprinters during acceleration (Johnson & Buckley, 2001: Journal of Sports Sciences, 19, 263 – 272) and distance runners at maximum velocity (Belli et al., 2002: International Journal of Sports Medicine, 23, 136 – 141), but not in sprinters at maximum velocity. The aim of this study was to quantify the joint power and work patterns of an elite sprinter during a ground-contact phase at maximum velocity to improve our understanding of the muscular control of the movement. Synchronized sagittal plane video (200 Hz) and ground reaction force (1000 Hz) data were obtained from one world-class male sprinter, who had given written informed consent, at 45 m of two 60-m maximal sprints (at velocities of 10.37 and 10.14 m s71). Metatarsophalangeal, ankle, knee, hip, and shoulder joint centres were manually digitized on the side of the ground leg and reconstructed using the two-dimensional direct linear transformation. All raw data were digitally filtered after residual analysis and joint power and work were calculated at the leg joints using conventional inverse dynamics equations. The hip extensors performed positive work early in stance (82 and 131 J). Positive work at the ankle (82 and 52 J) began in both trials approximately 0.015 s before it ceased at the hip. Positive work occurred at the knee (11 and 15 J) soon after touchdown, but was negligible for the remainder of stance. The timings of knee power phases were inconsistent between trials. Ankle and hip patterns mostly supported previous findings, but the lack of major positive knee extensor work in late stance did not (Belli et al., 2002; Johnson & Buckley, 2001). Johnson and Buckley (2001) suggested the powerful knee extension propelled the body forwards rather than upwards, but it has been suggested that, at maximum velocity, vertical not horizontal force production is crucial (Mann, 1985: In The elite athlete, edited by N. Butts, T. Gushiken, & B. Zarins. Jamaica, NY: Spectrum Publications). The generally low power measured at the knee suggests a stabilizing and compensatory, rather than power-producing, role for the joint, which may be linked to the specific demands of maximum velocity sprinting, presented by Mann (1985). Future studies will determine whether these characteristics are specific to the athlete studied, or are typical of all elite sprinters at maximum velocity.